1. Field of the Invention
The invention relates to a multi-roll table ring-rolling mill that comprises at least one main roll and two mandrel rolls, which are mounted in a mandrel roll table that rotates about a mandrel roll table axle, wherein the main roll rotates about a main roll axle, and the main roll axle and the mandrel roll table axle are mounted in unchangeable manner and eccentric to one another, at least during the rolling process. Likewise, the invention relates to a method for rolling rings in a multi-roll table ring-rolling mill, in which at least two mandrel rolls mounted in a mandrel roll table rotate about a main roll, wherein a roll gap formed between the mandrel rolls and the main roll, in each instance, is reduced as a function of the angular position of the mandrel roll table that exists with reference to the main roll, down to a roll gap minimum, and subsequently increased again.
2. Description of the Related Art
There are ring-rolling mills in different sizes, whereby for very large rings, a main roll and a mandrel roll are generally pressed against one another, and the ring to be rolled circulates in the roll gap situated between these two rolls. Depending on the specific requirements, axial rolls and/or further special rolls are also provided in the case of very large ring-rolling mills. In this connection, the rolling process as well as the degrees of deformation can be selected relatively freely, because ultimately, the ring can be passed through the respective roll gaps as often as desired. Such ring-rolling mills have a relatively complex construction, however, and are therefore cost-intensive, whereby the method sequence can also be complex and, in particular, very time-consuming. Such ring-rolling mills are known, for example, from DE 25 04 969 A1 or from DE 10 2011 108 113 A1.
Multi-roll table ring-rolling mills in which at least two, generally however at least four, mandrel rolls are mounted on a mandrel roll table that can rotate about a main roll can achieve significantly higher throughput. Such an arrangement is disclosed, for example, in DE 26 15 802 A1, in which, because of the placement of multiple mandrels on a mandrel roll table, each individual rolling process, however, can be configured individually for each of the rings, corresponding to the ring-rolling mills described above, by means of individual placement of the respective mandrel roll with reference to the main roll. Because of the mandrel roll table, the feed of rings to be rolled or ring blanks and the discharge of the rolled rings can be significantly accelerated and integrated into the rolling process.
Very high production speeds are allowed by multi-roll table ring-rolling mills such as those disclosed in DE 10 98 481 B, for example, whereby the multi-roll table ring-rolling mill presented there comprises a main roll and four mandrel rolls, which are mounted in a mandrel roll table rotating about a mandrel roll table axle, and whereby the main roll rotates about a main roll axle, and the main roll axle and the mandrel roll table axle are mounted in unchangeable manner and eccentric to one another, at least during the rolling process, and a roll gap formed is reduced down to a roll gap minimum, solely by means of changing the angular position of the mandrel roll table with reference to the main roll. After having passed through the roll gap minimum, the roll gap increases again, so that the rolling process is then completed. For refitting purposes, it is possible to change the location of the mandrel rolls on the mandrel roll table of DE 10 98 481 B. As DE 26 15 802 A2 also emphasizes in its discussion of DE 10 98 481 B, however, unavoidable variations in the insertion volume of the ring blanks or of the rings still to be rolled directly lead to variations in the diameter and the height, which then leads to extraordinarily complicated production systems, because generally calibration presses for the diameter, and frequently even further calibration presses for the required ring height have to be added subsequently.